| ABSTRACT: | THROUGH SKIN IMAGING for AIRCRAFT ASSEMBLY using PULSED - TRANSIENT
THERMOGRAPHY
D.Almond, and N. Avdelidis
University Of Bath, Bath, United Kingdom
An investigation has been made of the potential of pulsed transient thermography for identifying the location
of fixtures beneath aircraft skins to facilitate accurate automated assembly operations. Experimental studies
have been made of 1.6mm thick aluminium skins and both 4mm and 2mm thick carbon fibre plastic (CFRP)
composite skins over both aluminium and composite struts that represent fixtures. For the CFRP cases, the
struts behind the skin can be easily imaged and centre line location determined to an accuracy of 0.5mm.
Greater difficulty is experienced in the aluminium case caused by sensitivity to the thermal contact
resistance between the surfaces. Modelling results show a thermal contact resistance between two high
thermal conductivity aluminium surfaces to have far greater effect on thermal image degradation than
between two lower thermal conductivity CFRP surfaces. A modest loading of aluminium parts, however,
reduces the effect of the thermal contact resistance and enables a sub-skin strut to be imaged and located to a
similar accuracy to that achieved with CFPR parts. The development of an instrument utilising this
technique to navigate an automated machine will be discussed.
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